So last night as im parking my gta i hear this loud bang from my pass front end. Get out and car is sitting on the tire, with the control arm on the inside of my rim.

the castle nut sheared off the cotter pin, (there was a piece left in the center hole) and tore the bottom half of the threads out of the castle nut. The ball joint stud itself was undamaged (was replaced a couple years ago) as was everything else minus a scratch in my rim thankfully.
I put the ball joint back into the spindle (I have lowering spindles) and a new castle nut and new cotter pin and drove it home.
problem. I'm now super nervous to drive it because I have no idea why it did this! Anyone heard or had anything like this happen before? I searched but only found a couple threads where cotter pins were forgotten. Thanks

 

seems like a lot of parts today from foreign countries come with sub-standard hardware. your better off to re-use the factory castle nut.
i was changing upper ball joints on a truck i have and read reviews of people having easily stripped hardware. i went and bought all new grade 8 hardware, then stuck the replacement bolts in a vise to see if they would have stripped or not? i'll bet i didnt put 15 ft lbs on them before they stripped !!! threw the castle nuts away and re-used the old factory ones.

 

Sounds more like to me the castle nuts wasn't torqued properly when the joint was installed ad the tapered connection was never seated completely. The assemby was loose and the castle nut was the only thing holding the joint together, and eventually it finally failed. replace it, tighten it and you should be good

 

Yea, I re-read the original post 3x trying to figure out what exactly happened.

I don't see how the ball joint nut would have backed off if it was properly installed even if the cotter pin was forgotten, and I don't see how you could have driven around with it loose and the taper not seated without knowing something was wrong/moving around, and for that matter, I'm not sure how the nut could have backed off to that point without messing up the threads.

Even if it was a cheap aluminum cotter pin as opposed to proper steel one (not sure why they even make the aluminum ones), it would take quite a bit of force to shear both sides of the cotter pin back the nut out with it installed, I can't imaging it happening if it was installed correctly to start with.

 

I had that happen to me quite a few years back when I first built up a car, exact same thing castle nut sheared off the cotter pin and catastrophic faliure crossing over rail road tracks at 20MPH. thankfully it did not happen the day before!!!! I was doing high speed runs tuning the upper RPM of the car at around 160MPH+. The entire front end was brand new and installed by me (20 year licensed mechanic). They where cheap Ebay parts and supplied to me and that was the last time I installed anything that cheap!

Long story short, I never figured out why it backed off but I do know the folowing day the entire front end got replaced with MOOG parts!

 

Got any enemies?? Sabotage??

 

Yea I bought the high quality stuff, is why i'm worried. I haven't ripped into the front end yet just parked it until the weekend.

No enemies lol, and I doubt sabotage

 

When I re-did my front end with a new k member and a arms I found one of the castle nuts holding on by like 1 thread and the cotter pin sheered off just like you describe...the ball joint stud was still pressed into the spindle and I still had to use the ball joint tool to get it out....didn't think too much about it till now...guess I'm lucky

 

Yea, since I posted I checked everything over nothing looked wrong. Put the ball joint back into the spindle and a new Castle nut and pin on it, been a few hundred kilometers since then and haven't had any issuse since. Checked on it a couple times and still nice and tight.

 

Did you ever figure out what happened. I just had the same exact same thing happen to me 10 minutes ago. No warning signs, wheel just folded under the van as I was turning around in the driveway. ball joint is still good but the crown nut and cotter pin are gone. The ball joint was replaced about 6 weeks ago and I'm sure I tightened it and put the cotter pin in. I can't understand how this is even possible.

 

Honestly, I think it was a faulty casting of the nut. The threads just ripped out, I've been driving it ever since with the same ball joint and a new nut and cotter pin.